Many images you see on the Internet today have undergone compression for various reasons. Image compression can benefit users by having pictures load faster and webpages use up less space on a Web host. Image compression does not reduce the physical size of an image but instead compresses the data that makes up the image into a smaller size.
File size reduction remains the single most significant benefit of image compression. Depending on what file type you're working with, you can continue to compress the image until it's at your desired size. This means the image takes up less space on the hard drive and retains the same physical size, unless you edit the image's physical size in an image editor. This file size reduction works wonderfully for the Internet, allowing webmasters to create image-rich sites without using much bandwidth or storage space.
Some electronic devices, such as computers or cameras, may load large, uncompressed images slowly. CD drives, for example, can only read data at a specific rate and can't display large images in real time. Also, for some webhosts that transfer data slowly, compressed images remain necessary for a fully functional website. Other forms of storage mediums, such as hard drives, will also have difficulty loading uncompressed files quickly. Image compression allows for the faster loading of data on slower devices.
When you compress an image, sometimes you will get image degradation, meaning the quality of the image has declined. If saving a GIF or PNG file, the data remains even though the quality of the image has declined. If you need to show a high-resolution image to someone, large or small, you will find image compression as a disadvantage.
With some common file types, such as JPEG, when an image shrinks in size the compression program will discard some of the photo's data permanently. To compress these images, you need to ensure you had an uncompressed backup before starting. Otherwise, you will lose the high quality of the original uncompressed image permanently.